Air Pollution Exposure in Infancy and Incidence of Atopic Dermatitis in Preschool-Aged Children

Background: Atopic dermatitis is the most common inflammatory skin condition in children, influenced by genetic and environmental factors. The role of air pollution in atopic dermatitis development is understudied, and it is unclear whether early-life air pollution is a target for primary prevention. We aimed to evaluate infancy exposure to fine particulate matter (PM 2.5 ), nitrogen dioxide (NO 2 ), and ozone (O 3 ) and atopic dermatitis at ages 4-6 years and assess modification by child sex or maternal education. Methods: We conducted a pooled, longitudinal cohort study on 1587 children in six US cities in the ECHO-PATHWAYS Consortium (2017-2023). Three atopic dermatitis and eczema outcomes were ascertained using standardized caregiver questionnaires, and outdoor pollutant concentrations in the first year of life were estimated using validated national spatiotemporal models. Multivariable Poisson regression models were used to examine associations between pollutants and outcomes, adjusted for confounders. Results: O 3 was associated with the primary outcomes of current and location-specific atopic dermatitis (aRR per 1-ppb increase = 1.07 [95% CI: 1.01-1.13] and 1.06 [95% CI: 0.99-1.13], respectively). No associations were evident for NO 2 or PM 2.5 , and there was little evidence of effect modification by sex. Associations between O 3 and outcomes were evident only in children of mothers with lower educational attainment. Conclusions: If confirmed, this suggests that reducing early-life O 3 exposure could mitigate child health disparities related to atopic dermatitis. Notably, O 3 concentrations were relatively low in this setting, suggesting that current regulatory standards may not adequately protect child health.